This invention relates to locating the economizer valve close to the economizer heat exchanger or otherwise increasing the volume of the economizer circuit line in a refrigeration cycle.
Economizer circuits are utilized in refrigeration cycles to provide increased cooling or heating capacity. As is known, a refrigeration cycle passes a refrigerant between a compressor, where it is compressed and to a condensor, where it is typically exposed to ambient air. From the condensor, the refrigerant passes through a primary expansion device and then to an evaporator. An environment to be cooled is cooled by the refrigerant passing through the evaporator. The refrigerant returns from the evaporator back to the compressor, and may pass through a suction throttling device on the way.
An economizer circuit is sometimes incorporated just downstream of the condensor. Essentially, a portion of the refrigerant leaving the condensor is tapped from the main flow line and passed through an economizer expansion device. An economizer heat exchanger or flash tank receives the fluid leaving the economizer expansion device, and further receives the main flow of refrigerant from the condensor before it enters the primary expansion device. A flash tank and an economizer heat exchanger are both known ways of transferring heat between two flow lines. For purposes of this application, the term xe2x80x9ceconomizer heat exchangerxe2x80x9d should be understood to include both a heat exchanger transferring heat between the two lines through pipes, or a flash tank. Both are heat exchangers used in economizer cycles, and both are known. The term xe2x80x9ceconomizer heat exchangerxe2x80x9d as utilized in this application and claims should thus be understood to include both. The refrigerant leaving the iconomizer, circuit expansion device cools the refrigerant in the main flow line prior to it reaching the primary expansion device. Thus, the refrigerant reaching the primary expansion device has been additionally pre-cooled, and greater cooling capacity of the evaporator is achieved.
The tapped refrigerant leaving the economizer expansion device passes through the economizer heat exchanger and is returned to the compressor. To control cooling or heating unit capacity, it is desirable to have the capability of turning the economizer circuit on or off. Thus, a shut-off economizer valve is typically positioned adjacent to the compressor. An economizer line connects this shut-off valve back to the economizer heat exchanger. A further portion of the economizer line extends through the short distance from the economizer shut-off valve to the compressor.
During operation of the compressor, when the economizer valve is closed, the economizer portion of the line dead ends at the valve. Thus compressed refrigerant is pumped back and forth between the closed valve and the compressor in the dead end portion of the economizer line. This has sometimes resulted in undesirable temperature rise in the economizer line. Due to the high temperatures, expensive shut-off valves capable of withstanding the high temperatures may have been required.
The present invention is directed to optimizing the position of the economizer shut-off valve, which has previously been positioned adjacent the compressor, or otherwise adding additional volume between the compressor and shut-off valve.
In a disclosed embodiment of this invention, the economizer shut-off valve is positioned closer to the economizer heat exchanger than it is to the compressor spaced from the compressor or additional volume is otherwise added into the economizer line. Thus, there is a relatively long or large volume economizer dead end portion between the shut-off valve and the compressor when the shut-off valve is closed.
In a most preferred embodiment, the shut-off valve is positioned directly adjacent to the economizer heat exchanger. Thus, it is preferred that the economizer shut-off valve be positioned within the 50% of the economizer line closest to the economizer heat exchanger. It is most preferred that the economizer shut-off valve be positioned in the line within 20% of the economizer heat exchanger in embodiments wherein the economizer shut-off valve is positioned downstream of the economizer heat exchanger. Stated another way, additional volume is added to the portion of the economizer line extending toward the compressor.
In other embodiments, the economizer shut-off valve is positioned upstream of the economizer expansion device.
Further, in yet another embodiment, the economizer expansion device is electronically controlled and utilized not only as the expansion device but also as a shut-off valve.
With each of the above-discussed embodiments, the length and/or volume of the dead end portion of the economizer line is greatly increased compared to the prior art. While one might expect that such a positioning could result in decreased efficiency or capacity, in fact, the reverse has proven true. Tests show that with the positioning of the economizer shut-off valve closer to the economizer heat exchanger, both compressor efficiency and capacity are increased. Further, because the efficiency of the compression process is increased, the discharge temperature of the refrigerant leaving the compressor is also reduced by a few degrees.
The temperature in the dead end portion of the economizer line is significantly reduced. In one test, the temperature was reduced from a high of 310xc2x0 F. to 200xc2x0 F. This allows the use of less expensive shut-off valves, which need not withstand the high temperatures of the prior art. Further, fire hazards, etc., are minimized.
If the economizer shut-off valve is positioned upstream of the expansion device, the valve will typically seal the liquid portion of the refrigerant. The liquid lines are smaller in diameter than vapor lines and are easier to seal, thus, an even less expensive valve can be utilized, as a valve to seal liquid can be smaller and less expensive than a vapor line valve.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.